Automobile headlights wherein a replaceable lamp unit is employed are known. Examples are illustrated in the below-identified patents:
U.S. Pat. No. 2,423,664 by E. RYDER
U.S. Pat. No. 2,750,491 by H. J. ANDERSON
U.S. Pat. No. 3,593,017 by P. CIBIE
U.S. Pat. No. 3,688,103 by H. DAUMULLER
U.S. Pat. No. 3,917,939 by H. J. SCHMIDT ET AL
U.S. Pat. No. 3,987,326 by G. LINDAE
U.S. Pat. No. 4,342,142 by Y. NEIDA ET AL
U.S. Pat. No. 4,344,119 by T. BERGOT
U.S. Pat. No. 4,412,273 by P. HELBIG ET AL
As stated, the instant invention is related to lamp units of the variety described above. In particular, the invention defines a replaceable lamp unit which provides both a hermetic seal for the unit within the headlight's reflector and, equally important, assures that the electric lamp utilized therewith will be maintained in strict alignment as is necessary in automotive headlights. By the term "hermetic seal" is meant a seal which prevents the passage of moisture, dust and other elements which can adversely affect the operation of the headlight. By way of example, excessive moisture entering the headlight can adversely affect the reflective coating typically utilized on the concave reflector of the headlight, and thus significantly reduce light output therefrom.
In addition to providing a hermetic seal, the replaceable lamp unit defined herein assures that alignment of the electric lamp employed therewith will be maintained. That is, alignment of the glass envelope of the lamp relative to the unit's holder is provided such that the filament structure within the envelope (typically either a singular coiled filament or two, spaced coiled filaments) will be accurately aligned relative to the optical axis of the headlight's reflector when the lamp unit is oriented within the reflector's rear opening. Such alignment is deemed critical to assure optimum headlight output in the direction(s) desired.
As also described herein, a preferred light source which constitutes an important part of the replaceable lamp unit defined herein is an electric lamp of the tungsten halogen variety. One example is shown in U.S. Pat. No. 3,829,719 (Westlund, Jr. et al), this patent assigned to the same assignee as the instant invention. In tungsten halogen lamps, the tungsten which constitutes the filament material is normally evaporated from the filament during lamp operation and combines with the halogen to form a gaseous halide, the halide preventing the tungsten from depositing on the internal wall of the lamp's glass envelope. Upon returning to the filament structure, the halide decomposes, resulting in the deposition of tungsten back onto the filament structure and the release of additional halogen gas to assure continuation of the cycle. The halogen cycle is well known in the art and lamps employing it have been used for some time. Several varieties are presently manufactured and sold by the assignee of the invention. In the case of the two beam (dual filament) lamp, a typical tungsten halogen lamp provides about 65 watts when operated at high beam and about 45 watts at low beam. As stated, it is critical that the filament structure of the lamp within an automobile headlight be precisely aligned relative to the reflector to provide optimum output of the finished headlight. As will be described below, such alignment constitutes an important feature of the replaceable lamp unit defined herein.